SiC Termination Field Zones Ion Implantation
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Solution Overview
Problem
Existing semiconductor devices face challenges in forming robust termination structures with smooth electric field distributions, particularly in silicon carbide substrates, due to low diffusion coefficients of dopant atoms, leading to steep pn junctions and high peak electric field strengths.
Innovation Solution
The method involves forming field zones in silicon carbide substrates through ion implantation, laterally modulating dopant distribution to create smooth horizontal dopant profiles that fall from a maximum concentration to 37% of the maximum within a distance of at least 100 nm, forming pn junctions with a drift layer, which reduces peak electric field strength and enhances device ruggedness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion implantation is used to form termination structures in silicon carbide substrates, then dopant distribution can be controlled, but the low diffusion coefficient of dopant atoms leads to steep pn junctions and high peak electric field strengths
Solution Approach 1:
The patent applies local quality by creating field zones with laterally modulated dopant concentrations within the termination region. The dopant concentration is varied locally to form a smooth gradient profile, with maximum concentration at the junction termination extension and decreasing concentration toward the drift region, thereby shaping the electric field distribution to reduce peak field strength while maintaining precise dopant placement control through ion implantation
Solution Approach 2:
The patent changes the dopant concentration parameter by forming field zones with a specific horizontal net dopant distribution that falls from maximum concentration Nmax to Nmax/e within at least 100 nm. This parameter change creates a smooth transition profile that reduces field crowding and peak electric field strength compared to conventional abrupt junctions, while the ion implantation process maintains precise control over the dopant distribution profile
2Reliability
If multiple implants, oxide step etching, multiple etched mesas or grayscale lithography are used to form robust termination structures, then termination structure robustness is improved, but process complexity increases
Solution Approach 1:
The patent merges multiple process steps into a single ion implantation process that forms the field zones with the required smooth dopant distribution profile. Instead of using separate steps for oxide step etching, multiple implants, or grayscale lithography, the invention achieves the same robust termination structure formation through one controlled ion implantation step with laterally modulated dopant distribution, thereby reducing process complexity while maintaining structure robustness
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces peak electric field strength by at least 50%, improves device reliability, and minimizes the impact of lithographic misalignment and external charges, resulting in more robust semiconductor devices with improved termination structures.
Implementation Method 1
field zones are formed by ion implantation, wherein by laterally modulating a distribution of dopants entering the silicon carbide substrate by the ion implantation, a horizontal net dopant distribution in the field zones is set to fall from a maximum net dopant concentration Nmax to Nmax/e within at least 100 nm
Data Source
AI summary
In termination regions of a silicon carbide substrate field zones are formed by ion implantation. By laterally modulating a distribution of dopants entering the silicon carbide substrate by the ion implantation, a horizontal net dopant distribution in the field zones is set to fall from a maximum net dopant concentration Nmax to Nmax/e within at least 200 nm, with e representing Euler's number. The field zones form first pn junctions with a drift layer.